dm-writecache: use bvec_kmap_local instead of bvec_kmap_irq

There is no need to disable interrupts in bio_copy_block, and the local
only mappings helps to avoid any sort of problems with stray writes
into the bio data.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20210727055646.118787-8-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/dm-writecache.c

@@ -1214,14 +1214,13 @@ static void memcpy_flushcache_optimized(void *dest, void *source, size_t size)
 static void bio_copy_block(struct dm_writecache *wc, struct bio *bio, void *data)
 {
 	void *buf;
-	unsigned long flags;
 	unsigned size;
 	int rw = bio_data_dir(bio);
 	unsigned remaining_size = wc->block_size;
 
 	do {
 		struct bio_vec bv = bio_iter_iovec(bio, bio->bi_iter);
-		buf = bvec_kmap_irq(&bv, &flags);
+		buf = bvec_kmap_local(&bv);
 		size = bv.bv_len;
 		if (unlikely(size > remaining_size))
 			size = remaining_size;
@@ -1239,7 +1238,7 @@ static void bio_copy_block(struct dm_writecache *wc, struct bio *bio, void *data
 			memcpy_flushcache_optimized(data, buf, size);
 		}
 
-		bvec_kunmap_irq(buf, &flags);
+		kunmap_local(buf);
 
 		data = (char *)data + size;
 		remaining_size -= size;